This prenatal mouse brain shows the distribution of microglia (from left to right, the hindbrain, midbrain, forebrain and neocortex). The yellow microglia bear markers indicating that they belong to ...

In the 1950s, Källén showed that the embryonic chick brain collapses if the notochord and anterior hindbrain are separated from the neuroepithelium. At the time, the resulting convoluted appearance of ...